Tests and diagnosis

An incompetent cervix can be detected only during pregnancy, and even then diagnosis can be difficult — particularly during a first pregnancy. To help diagnose an incompetent cervix, your health care provider will document any symptoms you're experiencing.

Also, your health care provider will ask about your medical history. Be sure to tell your health care provider if you've experienced second trimester pregnancy loss or you had a cervical tear during a previous labor and delivery.

Your health care provider might determine you have an incompetent cervix if you have:

A history of painless cervical dilation and second trimester deliveries

A history of short labors and progressively earlier deliveries in previous pregnancies

Tests and procedures to help diagnose an incompetent cervix during the second trimester include:

Transvaginal ultrasound. If the fetal membranes aren't in your cervical canal or vagina, your health care provider will use transvaginal ultrasound to evaluate the length of your cervix, determine how much your cervix has dilated and examine the fetal membranes. During this type of ultrasound, a slender transducer is placed in your vagina to send out sound waves and gather the reflections of your cervix and lower uterus on a monitor.

Pelvic exam. Your health care provider will examine your cervix to see if the amniotic sac has begun to protrude through the opening (prolapsed fetal membranes). If the fetal membranes are in your cervical canal or vagina, you have an incompetent cervix.

Your health care provider will check for evidence of any congenital conditions or cervical tears that might cause an incompetent cervix. Your health care provider will also check for contractions and, if necessary, monitor them.

Lab tests. If the fetal membranes are visible and an ultrasound shows signs of inflammation but you don't have symptoms of an infection, your health care provider might test a sample of amniotic fluid (amniocentesis) to diagnose or rule out an infection of the amniotic sac and fluid (chorioamnionitis).

There aren't any tests that can be done before pregnancy to reliably predict an incompetent cervix. However, certain tests done before pregnancy can help detect uterine abnormalities that might cause an incompetent cervix.

For example, your health care provider might suggest an ultrasound or magnetic resonance imaging (MRI) — a procedure that uses a magnetic field and radio waves to create detailed images of the organs and tissues within your body. In some cases, hysterosalpingography — a procedure that uses X-rays to examine the inside of the uterus, fallopian tubes and surrounding area — is recommended.

What can I do to promote a healthy pregnancy? National Institute of Child Health and Human Development. http://www.nichd.nih.gov/health/topics/preconceptioncare/conditioninfo/pages/healthy-pregnancy.aspx. Accessed Dec. 18, 2014.

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